Steps added to density calculator

[singhnaveen098]

Steps added to density calculator in the physics section.

Related Issue

• Info about Issue or bug

Fixes: #463

Describe the changes you've made

Steps added to density calculator in the physics section.

A clear and concise description of what you have done to successfully close your assigned issue. Any new files? or anything you feel to let us know!

Checklist:

• [x] My code follows the style guidelines of this project.
• [x] I have performed a self-review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.

Screenshots

| Original

| Updated

original screenshot	updated screenshot

[github-actions[bot]]

Our team will soon review your PR. Thanks @singhnaveen098 :)

[github-actions[bot]]

Thank you @singhnaveen098 for taking out your valuable time in order to contribute to our project. Looking forward for more such amazing contributions :).